Package com.google.ortools.constraintsolver

Class PathOperator

java.lang.Object

com.google.ortools.constraintsolver.BaseObject

com.google.ortools.constraintsolver.LocalSearchOperator

com.google.ortools.constraintsolver.IntVarLocalSearchOperator

com.google.ortools.constraintsolver.PathOperator

public class PathOperator
extends IntVarLocalSearchOperator

Base class of the local search operators dedicated to path modifications
(a path is a set of nodes linked together by arcs).
This family of neighborhoods supposes they are handling next variables
representing the arcs (var[i] represents the node immediately after i on
a path).
Several services are provided:
- arc manipulators (SetNext(), ReverseChain(), MoveChain())
- path inspectors (Next(), Prev(), IsPathEnd())
- path iterators: operators need a given number of nodes to define a
neighbor; this class provides the iteration on a given number of (base)
nodes which can be used to define a neighbor (through the BaseNode method)
Subclasses only need to override MakeNeighbor to create neighbors using
the services above (no direct manipulation of assignments).

Field Summary

Fields inherited from class com.google.ortools.constraintsolver.BaseObject

swigCMemOwn

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	PathOperator(long cPtr, boolean cMemoryOwn)
	PathOperator(IntVar[] next_vars, IntVar[] path_vars, int number_of_base_nodes, boolean skip_locally_optimal_paths, boolean accept_path_end_base, java.util.function.LongToIntFunction start_empty_path_class, SWIGTYPE_p_std__functionT_std__vectorT_int_t_const_Rfint_intF_t get_neighbors)
	PathOperator(IntVar[] next_vars, IntVar[] path_vars, SWIGTYPE_p_operations_research__PathOperator__IterationParameters iteration_parameters)	Builds an instance of PathOperator from next and path variables.

Method Summary

Modifier and Type	Method	Description
protected boolean	ConsiderAlternatives(long base_index)	Indicates if alternatives should be considered when iterating over base nodes.
void	delete()
protected void	finalize()
protected long	getBaseNodeRestartPosition(int base_index)	Returns the index of the node to which the base node of index base_index must be set to when it reaches the end of a path. By default, it is set to the start of the current path. When this method is called, one can only assume that base nodes with indices < base_index have their final position.
protected static long	getCPtr(PathOperator obj)
protected boolean	initPosition()	Returns true if the operator needs to restart its initial position at each call to Start()
boolean	neighbor()
protected boolean	oneNeighbor()	This method should not be overridden.
protected void	OnNodeInitialization()	Called by OnStart() after initializing node information.
protected boolean	onSamePathAsPreviousBase(long base_index)	Returns true if a base node has to be on the same path as the "previous" base node (base node of index base_index - 1). Useful to limit neighborhood exploration to nodes on the same path. it's currently way more complicated to implement.
long	Prev(long node)	Returns the node before node in the current delta.
void	reset()
protected boolean	restartAtPathStartOnSynchronize()	When the operator is being synchronized with a new solution (when Start() is called), returns true to restart the exploration of the neighborhood from the start of the last paths explored; returns false to restart the exploration at the last nodes visited. This is used to avoid restarting on base nodes which have changed paths, leading to potentially skipping neighbors.
protected void	setNextBaseToIncrement(long base_index)	Set the next base to increment on next iteration.
protected void	swigDirectorDisconnect()
protected static long	swigRelease(PathOperator obj)
void	swigReleaseOwnership()
void	swigTakeOwnership()

Methods inherited from class com.google.ortools.constraintsolver.IntVarLocalSearchOperator

activate, activated, addVars, ApplyChanges, deactivate, getCPtr, HoldsDelta, isIncremental, oldValue, onStart, PrevValue, RevertChanges, setValue, size, SkipUnchanged, start, swigRelease, value, var

Methods inherited from class com.google.ortools.constraintsolver.LocalSearchOperator

getCPtr, HasFragments, nextNeighbor, swigRelease

Methods inherited from class com.google.ortools.constraintsolver.BaseObject

getCPtr, swigRelease, toString

Methods inherited from class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

PathOperator

protected PathOperator(long cPtr,
                       boolean cMemoryOwn)

PathOperator

public PathOperator(IntVar[] next_vars,
                    IntVar[] path_vars,
                    SWIGTYPE_p_operations_research__PathOperator__IterationParameters iteration_parameters)

Builds an instance of PathOperator from next and path variables.

PathOperator

public PathOperator(IntVar[] next_vars,
                    IntVar[] path_vars,
                    int number_of_base_nodes,
                    boolean skip_locally_optimal_paths,
                    boolean accept_path_end_base,
                    java.util.function.LongToIntFunction start_empty_path_class,
                    SWIGTYPE_p_std__functionT_std__vectorT_int_t_const_Rfint_intF_t get_neighbors)

Method Detail

getCPtr

protected static long getCPtr(PathOperator obj)

swigRelease

protected static long swigRelease(PathOperator obj)

finalize

protected void finalize()

Overrides:

finalize in class IntVarLocalSearchOperator

delete

public void delete()

Overrides:

delete in class IntVarLocalSearchOperator

swigDirectorDisconnect

protected void swigDirectorDisconnect()

Overrides:

swigDirectorDisconnect in class IntVarLocalSearchOperator

swigReleaseOwnership

public void swigReleaseOwnership()

Overrides:

swigReleaseOwnership in class IntVarLocalSearchOperator

swigTakeOwnership

public void swigTakeOwnership()

Overrides:

swigTakeOwnership in class IntVarLocalSearchOperator

neighbor

public boolean neighbor()

reset

public void reset()

Overrides:

reset in class LocalSearchOperator

Prev

public long Prev(long node)

Returns the node before node in the current delta.

oneNeighbor

protected boolean oneNeighbor()

This method should not be overridden. Override MakeNeighbor() instead.

Overrides:

oneNeighbor in class IntVarLocalSearchOperator

OnNodeInitialization

protected void OnNodeInitialization()

Called by OnStart() after initializing node information. Should be
overridden instead of OnStart() to avoid calling PathOperator::OnStart
explicitly.

restartAtPathStartOnSynchronize

protected boolean restartAtPathStartOnSynchronize()

When the operator is being synchronized with a new solution (when Start()
is called), returns true to restart the exploration of the neighborhood
from the start of the last paths explored; returns false to restart the
exploration at the last nodes visited.
This is used to avoid restarting on base nodes which have changed paths,
leading to potentially skipping neighbors.

onSamePathAsPreviousBase

protected boolean onSamePathAsPreviousBase(long base_index)

Returns true if a base node has to be on the same path as the "previous"
base node (base node of index base_index - 1).
Useful to limit neighborhood exploration to nodes on the same path.
it's currently way more complicated to implement.

getBaseNodeRestartPosition

protected long getBaseNodeRestartPosition(int base_index)

Returns the index of the node to which the base node of index base_index
must be set to when it reaches the end of a path.
By default, it is set to the start of the current path.
When this method is called, one can only assume that base nodes with
indices < base_index have their final position.

setNextBaseToIncrement

protected void setNextBaseToIncrement(long base_index)

Set the next base to increment on next iteration. All base > base_index
will be reset to their start value.

ConsiderAlternatives

protected boolean ConsiderAlternatives(long base_index)

Indicates if alternatives should be considered when iterating over base
nodes.

initPosition

protected boolean initPosition()

Returns true if the operator needs to restart its initial position at each
call to Start()